SPATIAL AND TEMPORAL PATTERNS IN PARTICLE DATA MEASURED DURING THE MOHAVE STUDY

Project MOHAVE (Measurement of Haze and Visual Effects) was conducted during 1992 to assess the contribution of the Mohave Power Project, ot her point sources, and regional emissions to visibility impairment in Grand Canyon National Park. One objective of Project MOHAVE was to det ermine the spatial and temporal patterns of aerosol concentrations dur ing summer and winter in the region. Patterns in the fine particle dat a were examined by time plots, spatial contour maps, and empirical ort hogonal function (EOF) analysis, which reduces all observed spatial pa tterns to a few that explain most of the variance. Results obtained du ring the summer differed from those obtained in the winter. However, d ifferences were not uniform across species. During the summer there wa s evidence of transport of sulfur, organic and light-absorbing carbon, and several trace elements from southern California into the study ar ea. Winter concentrations of several species, including sulfur, seleni um, and organic and light-absorbing carbon, were higher within the can yon than on the rim, probably because emissions from local sources sta gnate within the canyon during the winter. Sources in and near Las Veg as, NV, influenced the concentrations of several species, especially a t sites to the north and east.